(1) Field of the Invention
The present invention relates to a pixel structure and, more particularly, to a structure which can facilitate to detect if there exists any residue.
(2) Description of the Prior Art
In general, a liquid crystal panel mainly comprises a light filter substrate, an array substrate, and a liquid crystal material layer filled between the light filter substrate and the array substrate. By controlling the electric field occurred between the array substrate and the light filter substrate, the direction of liquid crystal molecules of the liquid crystal layer can be twisted to change the path of light transmitting in the liquid crystal panel. Thereby, each of the light beams transmitting out the filter substrate can present particular brightness and thus a respective image corresponding to the incident light control can be displayed.
FIG. 1 shows a schematic top-view of an array substrate 1 in the liquid crystal display.
The array substrate 1 has a plurality of scan lines 10 and data lines 11. The scan lines 10 and data lines 11 are substantially interlaced with each other. Upon such an arrangement, the array substrate 1 is divided into a plurality of pixel structures 12, each of the pixel structures 12 has a thin film transistor 121 and a pixel electrode 122. Wherein, the thin film transistor 121 is a three-terminal switch electrically connected to the scan line 10, the data line 11, and the pixel electrode 122. The thin film transistor 121 can be turned on or turned off according to the input electric signals form the scan lines 10, and thereby to control the voltage signal transmitted from the data line 11 to the pixel electrode 122.
Besides, the scan lines 10, the data lines 11, the thin film transistor 121, and the pixel electrode 122 are all fabricated through respective depositing processes and etching processes so as to have various materials formed on the array substrate 1 in sequence by predetermined patterns. During the fabrication processes, residues may still remain outside the predetermined patterns, and thereby may lead to various defects.
For instance, FIG. 2 shows a schematic top-view of a pixel structure 12. Wherein the thin film transistor 121 is fabricated, an amorphous silicon material is disposed on a gate 1211 acting as a channel layer 1212 of the transistor 121. If the amorphous silicon material is not disposed in the predetermined position, the possible residues 13 would be formed to remain in the pixel structure as shown in FIG. 2. Else, the external materials may also be dropped onto the pixel structure and cause the residue 13.
If the residue 13 were located at an overlap region of the data line and the pixel electrode 122, a coupled capacitance will be generated between the residue 13 and the pixel electrode 122 located on the residue 13. While the array substrate 11 is operated and a voltage level is applied to the scan line 10 and the data line 11, the voltage of the data line 11 can cross the residue 13 so as to have the pixel electrode 122 to generate a coupled capacitance to affect common operation of the pixel electrode 122, and thereby a possible point defect can be introduced.
In FIG. 3, a schematic top-view of another pixel structure is shown. When a metal layer is deposited on the array substrate to form a plurality of the scan lines 10, and when a metal material is disposed outside the predetermined position, a residue 13 in the pixel structure would be formed, as shown in FIG. 3. If the residue 13 just happens to connect two scan lines 10, a short circuit leading to a line defect would be inevitable.
Accordingly, the above-mentioned residue 13 can become one of major reasons that cause defects on a liquid crystal panel. The currently testing method is to input a voltage across the scan lines and the data lines, to measure the voltage of each of the pixel electrodes, and then to compare if there exists any abnormal voltage at any one of the pixel electrodes. However, this testing exists a major drawback. In the above-mentioned pixel structure, a coupled capacitance circumstance is not enough to affect the voltage of the pixel electrode. Namely, it is difficult to sensitively detect the difference of voltages between the pixel electrodes with the coupled capacitance and those without the coupled capacitance. Thus, it is unable to identify whether or not the pixel structure contains an unnecessary residue, which causes the coupled capacitance.
If the residue remains in the pixel structure, a short circuit would exist between two adjacent scan lines. After a voltage is fed into the scan lines and the data lines of the device that meets a short circuit, all the response voltages measured at the pixel electrodes connected to the scan lines would become abnormal. However, the difference of the response voltages at the pixel electrodes would be extremely small. In other words, even that the short circuit between two adjacent scan lines can be located, it is still difficult to verify which pixel electrode has the residue causing the short circuit.
Hence, for the ordinary skilled people in the art, how to effectively detect the unnecessary residues on array substrates so as to prevent from the defect problems resulted from the residues is one of the main topics in the industrial circles.